1. Field of the Invention
The invention in general relates to a tethered aerostat system, and in particular to a lighting device carried by the tether when the tether is utilized as an antenna for a transmitter.
2. Background Information
Tethered aerostats are commonly used as high altitude platforms for electronic equipment such as radar, communications, relay stations etc. The aerostat, which is an aerodynamically shaped lighter-than-air balloon is held on station and is securely connected to a ground based mooring system by means of a high-strength, light-weight electromechanical tether.
In order to make the tether visible to passing aircraft, lights such as strobe lights are placed along the tether at predetermined intervals during the deployment of the aerostat. Typically, battery operated strobe lights are limited to about 50 hours of operation after which the battery packs must be recharged. In addition, once deployed, the strobe lights cannot be turned off from the ground. Accordingly, for conventional aerostat systems a method has been proposed whereby power may be coupled to the strobe lights via transformer action utilizing a core and the electrically conducting portion of the tether as a one turn primary winding and to which is connected, at the ground mooring system, a signal generator supplying electrical power. The circuit is completed through the tether capacity to ground.
In addition to its use as a high altitude platform, the aerostat arrangement may also be used as a high power VLF communication system with the electrical portion of the tether acting as the antenna. It would be desirable to operate strobe lights on the antenna similar to those on the conventional aerostat system, however, if the VLF transmitter current is utilized to supply power to the strobe lights, the conventional circuitry for powering the strobe lights cannot handle the wide range of tether currents and frequencies as may be encountered in the VLF transmitter application.
Accordingly, it is an object of the present invention to provide for lighting apparatus for the tether of an aerostat and which will be operative when the tether is utilized as the antenna when the system is operating in a transmitter mode of operation.